Iron(II)/Reductant (DH2)-Induced Activation of Dioxygen for the Hydroxylation of Aromatic Hydrocarbons and Phenols: Reaction Mimic for Tyrosine Hydroxylase

Hage, John P.; Sawyer, Donald T.

doi:10.1021/ja00126a001

Cited by 15 publications

(16 citation statements)

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“…61,62 The use of iron porphyrins as model catalysts has allowed for further understanding of the significant steps involved in many enzymatic oxidation reaction mechanisms. 63 More recently, Machii et al 57 demonstrated the use of a (TMP)Fe III (RCO 2 ), where TMP is 5,10,15,20-tetramesitylporphyrin, complex for the epoxidation of norborylene and R-methylstyrene at -78°C with a variety of peracids. This research has suggested the OdFe IV (TMP) π-cation radical as being the active oxidant for the epoxidation reaction.…”

Section: Resultsmentioning

confidence: 99%

Selective Oxidation in Supercritical Carbon Dioxide Using Clean Oxidants

Sahle‐Demessie

Gonzalez

Enriquez

et al. 2000

Ind. Eng. Chem. Res.

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We have systematically investigated heterogeneous catalytic oxidation of different substrates in supercritical carbon dioxide (SC-CO 2 ). Three types of catalysts, a metal complex {cis-[Fe-(dmp) 2 (H 2 O) 2 ] (CF 3 SO 3 ) 2 } (dmp ) 2,9-dimethyl-1,10-phenanthroline), 0.5% platinum γ-alumina, and 0.5% palladium γ-alumina, were used at a pressure of 200 bar, at temperatures from 60 to 150°C, and for 3-18 h for partial oxidation of organic substrates. The metal-oxo catalyst used gave as high as 3.9% conversion of cycloxene to its oxides and epoxides, with the major products being the ketone and alcohol. The oxidation of cyclohexene strongly depended on the concentration of oxygen, whereas length of reaction (3-18 h) and temperature (60-150°C) were shown to be less significant on the conversion and selectivity of the reaction. Oxidation of cyclohexene over Pd and Pt/Al 2 O 3 catalysts resulted in a mixture of dehydrogenation and oxygenated products.

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Section: Resultsmentioning

confidence: 99%

Selective Oxidation in Supercritical Carbon Dioxide Using Clean Oxidants

Sahle‐Demessie

Gonzalez

Enriquez

et al. 2000

Ind. Eng. Chem. Res.

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Section: Evidence From Comparative Studies With Mononuclear Nonheme Imentioning

confidence: 99%

“…The mechanistic scheme for such reactions embodies the occurrence of a ternary catalyst/reductant/O 2 adduct [258] analogous to P450 chemistry, so that more concerted redox steps can be envisioned. Substrate transformation posits the participation of structurally similar hydroperoxo‐iron catalysts with different formal oxidation states [258,260], the process being driven to exothermicity via water formation (. Electrochemical investigations support this concept, revealing autoxidation of diphenylhydrazine, when exposed to O 2 , to liberate hydrogen peroxide, which collapses with iron(II) to give an Fe(II)‐H 2 O 2 complex directly leading to metabolic turnover [261].…”

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confidence: 99%

“…Finally, combination, in the presence of atmospheric dioxygen, of a relatively labile Fe(II) complex such as bis (2,2′‐bipyridine)iron(II), bis(picolinate) iron(II), or bis(dipicolinate)iron(II) with a reductant such as diphenylhydrazine to constitute a so‐called Mimoun system [257] has been shown to provide a useful tool to assess the molecular basis of alkane [258,259] and phenol [260] hydroxylation. The mechanistic scheme for such reactions embodies the occurrence of a ternary catalyst/reductant/O 2 adduct [258] analogous to P450 chemistry, so that more concerted redox steps can be envisioned.…”

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confidence: 99%

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Models and mechanisms of O‐O bond activation by cytochrome P450

Hlavica¹

2004

European Journal of Biochemistry

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Cytochrome P450 enzymes promote a number of oxidative biotransformations including the hydroxylation of unactivated hydrocarbons. Whereas the long-standing consensus view of the P450 mechanism implicates a high-valent ironoxene species as the predominant oxidant in the radicalar hydrogen abstraction/oxygen rebound pathway, more recent studies on isotope partitioning, product rearrangements with Ôradical clocksÕ, and the impact of threonine mutagenesis in P450s on hydroxylation rates support the notion of the nucleophilic and/or electrophilic (hydro) peroxo-iron intermediate(s) to be operative in P450 catalysis in addition to the electrophilic oxenoid-iron entity; this may contribute to the remarkable versatility of P450s in substrate modification. Precedent to this mechanistic concept is given by studies with natural and synthetic P450 biomimics. While the concept of an alternative electrophilic oxidant necessitates C-H hydroxylation to be brought about by a cationic insertion process, recent calculations employing density functional theory favour a Ôtwo-state reactivityÕ scenario, implicating the usual ferryl-dependent oxygen rebound pathway to proceed via two spin states (doublet and quartet); state crossing is thought to be associated with either an insertion or a radicalar mechanism. Hence, challenge to future strategies should be to fold the disparate and sometimes contradictory data into a harmonized overall picture.

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“…8 It has been known that activated oxygen interacts with organic substrates via H-atom and O-atom transfer. 14,15 In Fenton chemistry, hydrocarbons are converted to ketones and alcohols in the presence of Fe(II) combined with a donor molecule such as HOOH or reagents like PhNHNHPh, ascorbic acid or PhCH 2 SH. [15][16][17] On the other hand, anhydrous covalent metal nitrates are known to be strong oxidants wherein the species responsible for the oxidation of organic compounds is the NO 3 radical produced by the dissociation of metal-nitrate bidentate bonds.…”

Section: Introductionmentioning

confidence: 99%